Impacts of electrolyzer design, operation, and measurement on ammonia electrosynthesis in aqueous and non-aqueous media
department or school: Applied Science, Faculty of
department or school: Chemical and Biological Engineering, Department of
data provider: DSpace
degree campus: UBCV
creator: Bi, Wei
issued: 2024-04-08T19:17:49Z
issued: 2024
related degree: Doctor of Philosophy - PhD
degree grantor: University of British Columbia
description: Ammonia (NH₃) is critical to sustaining agriculture for the rapid growth of global population. This thesis focuses on NH₃ electrosynthesis via the electrochemical nitrogen reduction reaction (ENRR) and develops customized flow electrolyzers for aqueous and non-aqueous ENRR conditions. The ENRR performance with commercial or research electrocatalysts was firstly evaluated in aqueous media, but the prevalence of false positives from contaminated cell components masked the genuine ENRR assessment. Contributing to the observed false positives, NH₃ or ammonium (NH₄⁺) crossover through the separator was then investigated. Despite frequent appearances in the literature, Nafion as a cation-exchange membrane is incapable of completely separating NH₃/NH₄⁺ and acts as a possible source or sink of contamination. The behaviors of NH₃/NH₄⁺ that include crossover, volatilization, and adsorption in Nafion were systematically evaluated under a variety of electrolyte compositions, operation conditions, concentration gradients, and feed locations. Additionally, an anion-exchange membrane and microporous polypropylene separators were evaluated as alternatives to the Nafion separator. However, only the hydrophobic Celgard separator demonstrates satisfactory NH₃/NH₄⁺ separation at open-circuit conditions. Lastly, a three-compartment cell was used to evaluate the non-aqueous lithium-mediated ENRR performance of gas-diffusion electrodes with a carbon-based reaction layer: carbon-supported Pt, carbon black, and graphite. The ENRR results achieved in tetrahydrofuran-based electrolyte can generally achieve one-order of magnitude higher NH₄⁺ concentration than in aqueous media, thus avoiding false positives. The current density (−5 mA cm⁻²) and the EtOH concentration (0.5 vol%) were optimized with a current-cycling operation strategy using the C45 carbon black cathode. Replacing the Nafion binder with polyvinylidene difluoride further improves the LNRR performance to 3.11 ± 0.41 μmol h⁻¹ cm⁻² …
aggregated CHO: https://circle.library.ubc.ca/rest/handle/2429/87708
note: IMPACTS OF ELECTROLYZER DESIGN, OPERATION, AND MEASUREMENT ON AMMONIA ELECTROSYNTHESIS IN AQUEOUS AND NON-AQUEOUS MEDIA by Wei Bi B.A., The University of British Columbia, 2019 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in THE FACULTY OF GRADUATE AND POSTDOCTORAL STUDIES (CHEMICAL AND BIOLOGICAL ENGINEERING) THE UNIVERSITY OF BRITISH COLUMBIA (Vancouver) March 2024 © Wei Bi, 2024 ii The following individuals certify that they have read, and recommend to the Faculty of Graduate and Postdoctoral Studies for acceptance, the dissertation entitled: Impacts of Electrolyzer Design, Operation, and Measurement on Ammonia Electrosynthesis in Aqueous and Non-aqueous Media submitted by Wei Bi in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Chemical and Biological Engineering Examining Committee: David P. Wilkinson, Professor, Chemical and Biological Engineering, UBC Co-supervisor Elöd Gyenge, Professor, Chemical and Biological Engineering, UBC Co-supervisor Vikramaditya G. Yadav, Associate Professor, Chemical and Biological Engineering, UBC Supervisory Committee Member Chester (David) Upham, Assistant Professor, Chemical & Biological Engineering, UBC University Examiner Jongho Lee, Associate Professor, Civil Engineering, UBC University Examiner Additional Supervisory Committee Members: Edouard Asselin, Professor, Materials Engineering, UBC Supervisory Committee Member iii Abstract Ammonia (NH3) is critical to sustaining agriculture for the rapid growth of global population. This thesis focuses on NH3 electrosynthesis via the electrochemical nitrogen reduction reaction (ENRR) and develops customized flow electrolyzers for aqueous and non-aqueous ENRR conditions. The ENRR performance with commercial or research electrocatalysts was firstly evaluated in aqueous media, but the prevalence of false positives from contaminated cell components masked the genuine ENRR assessment. Contributing t…
has type: Thesis/Dissertation
date issued: 2024-05
is shown at: 10.14288/1.0441010
language: eng
degree discipline: Chemical and Biological Engineering
provider: Vancouver : University of British Columbia Library
publisher: University of British Columbia
rights: Attribution-NonCommercial-NoDerivatives 4.0 International
rights URI: http://creativecommons.org/licenses/by-nc-nd/4.0/
scholar level: Graduate
contributor: Wilkinson, David P.
contributor: Gyenge, Előd
type: Text
identifier URI: http://hdl.handle.net/2429/87708